infoschema: Support for showing "AUTO_INCREMENT" in "information_schema.tables"

[zimulala]

What have you changed? (mandatory)

Fix #6973

tidb>create table t(id int auto_increment primary key, c int);
Query OK, 0 rows affected (0.11 sec)

tidb>insert into t values(1,1);
Query OK, 1 row affected (0.10 sec)

tidb>insert into t values(10000,1);
Query OK, 1 row affected (0.01 sec)

tidb>select * from t;
+-------+------+
| id    | c    |
+-------+------+
|     1 |    1 |
| 10000 |    1 |
+-------+------+
3 rows in set (0.00 sec)

select auto_increment from information_schema.tables where table_name = 't';

before :

+----------------+
| auto_increment |
+----------------+
|             0 |
+----------------+
1 row in set (0.00 sec)

after :

+----------------+
| auto_increment |
+----------------+
|          30002 |
+----------------+
1 row in set (0.00 sec)

What is the type of the changes? (mandatory)

• Bug fix (non-breaking change which fixes an issue)

How has this PR been tested? (mandatory)

Unit test

Does this PR affect documentation (docs/docs-cn) update? (mandatory)

No

Does this PR affect tidb-ansible update? (mandatory)

No

Does this PR need to be added to the release notes? (mandatory)

release note:
Support for showing "auto_increment" in "information_schema.tables".

[zimulala]

/run-all-tests

[XuHuaiyu]

why this return 30002?

[ciscoxll]

@zimulala Allocate a batch of 30000 AUTO_INCREMENT?

[zimulala]

@XuHuaiyu
Because the next global auto ID is 30002.
We can do some operations as follows:
TiDB 1

tidb> create table t(`id` int(11) NOT NULL AUTO_INCREMENT,`c` int(11) DEFAULT NULL, PRIMARY KEY (`id`));
Query OK, 0 rows affected (0.13 sec)

tidb> insert into t values(1,1);
Query OK, 1 row affected (0.14 sec)

tidb> insert into t values(10000,1);
Query OK, 1 row affected (0.02 sec)

tidb> select * from t;
+-------+------+
| id    | c    |
+-------+------+
|     1 |    1 |
| 10000 |    1 |
+-------+------+
2 rows in set (0.01 sec)

TiDB 2
Then we do the operation as follows:

tidb> insert into t values();
Query OK, 1 row affected (0.13 sec)

tidb> select * from t;
+-------+------+
| id    | c    |
+-------+------+
|     1 |    1 |
| 10000 |    1 |
| 30002 | NULL |
+-------+------+
3 rows in set (0.01 sec)

[zimulala]

@ciscoxll
Yes.

[XuHuaiyu]

can break here?

[ciscoxll]

@zimulala Please change here.

[zz-jason]

@zimulala please add the "release-note" label for this PR

[zimulala]

PTAL @XuHuaiyu @ciscoxll

[ciscoxll]

LGTM

[zz-jason]

LGTM

[zz-jason]

/run-all-tests